Indoor hyacinths - can I plant them outside at some point?

My MIL gave us a basket thing with 5 hyacinth bulbs in it. The flowers have been and gone. Can they be planted outside to flower next year or do we just need to bin them? If they can be planted outside, what do we need to do to them now and when can they go out?

I assume the foliage/old flower heads are still intact? Leave the foliage, but cut off the seed head to let strength go back into the bulbs.

Yes, they can be planted at anytime. Ideally put them where they won't be accidentally disturbed or dug out again (by you, children, animals). The better the soil/compost they go into, the better they should do next year. Somewhere that doesn't get waterlogged, or dry out TOO much in summer. If there are any 'baby' bulbs at the side of the original parent bulbs, they can be broken off and planted separately, but it may be several years before they build up.

Potted bulbs that flower in winter are specially raised to give their best the first year. Subsequent years they may not be as strong, paler colour, and even revert to how they would have been in the wild.

Some people might suggest drying the bulbs and storing, to plant later in the year, but I always think let them be in soil, and living a 'natural' life with frosts, etc which shouldn't harm them.

I planted some last year and they are coming up and seem to be single spikes (some writers say you get lots of little spikes). I think I just bunged them in - ie I didn't give them anything special in the way of food.

I've been planting them out after flowering for years now, as Ferguson says, usually into old containers which can spend rest of the year mostly out of sight, and they do usually flower for a few more years, getting smaller. It's worthwhile giving the foliage couple of doses of feed before letting it die down naturally, having cut down dead flowers.